The vibrational and conformational properties exhibited by CHsCH2C(=S)SCHs and CH~CH~C(=S)SCHZCH3
were studied by Raman and infrared spectroscopies for the liquid and solid phases, and by ab initio
calculations for the isolated molecule. It is shown that these molecules tend to adopt nonsymmetricconformations
near the C(=S)S group, in contrast to their oxygen analogues whose most stable conformers correspond to
structures having a planar skeleton. For the conformers differing by internal rotation about the C,-C bond,
the most stable conformer-the skew form having the CC-C=S dihedral angle equal to flOOO-is more
stable than the symmetric syn conformer (CC-C=S equal to Oo) by ca. 1.0 kJ mol-'. In the annealed solid,
CH3CH*-C(=S)SCH3 exists in the skew conformation, which is also the most stable form in the liquid and
isolated molecule. As the liquid is rapid-froze, a glassy state where both conformers exist is obtained, which
enables a spectroscopic characterization of the less stable syn form, taking advantage of the usual solid-state
band-narrowing effect. The conformational dependence of some relevant structural parameters was used to
characterize the most important intramolecular interactions present in the various conformers. In addition,
the ab initio vibrational spectra were calculated and used for the assignment of the experimentally observed
bands. In particular, the Raman and IR spectra of the molecules in the liquid and solid phases were assigned
and the results were used to explain details of the resonance Raman spectra of methyl dithiopropionate [Ozaki,
Yo;St orer, A. C.; Carey, P. R. Can J. Chem. 1982, 60, 1901